Digital signal measuring apparatus and traffic observing method

ABSTRACT

Abstract of Disclosure 
     A digital signal measuring apparatus comprises a bus probe unit for extracting a bus event occurring on a bus based on a digital bus signal on the bus of the system to be measured, a traffic measuring unit for counting the number of occurrences of bus event based on the occurrence information of the extracted bus event, and a console unit for acquiring and processing the count value of the traffic measuring unit.

Background of Invention

[0001]Field of the invention

[0002] The present invention relates to a digital signal measuringapparatus and its observing method for observing the signal traffic on abus of a system to be measured.

[0003]Background of the invention

[0004] Conventionally, the observation and evaluation of a digital busare generally performed in the following way.

[0005] While using a digital signal measuring apparatus such as a logicanalyzer, a bus is probed and triggered with a predetermined buspattern, then a digital bus signal is acquired, and the obtained data ofdigital bus signal is stored in a digital storage equipped for the logicanalyzer. At the same time, the measurement result of this digitalsignal is displayed in waveform on a display.

[0006] In the case where the measurement result is observed and analyzedin detail, an analysis program is executed for the acquired data storedin the digital storage on a computer.

[0007] A conventional digital signal measuring apparatus for observingthe digital bus is exemplified below.

[0008]Figure 8 is a block diagram illustrating the configuration of thelogic analyzer. In the same figure, two logic analyzers 810A and 810Bare shown to observe two buses 820A and 820B, each logic analyzer havingthe same configuration.

[0009] Referring to Figure 8, the logic analyzers 810A and 810B areconnected to the probes 830 for acquiring a digital bus signal from thebuses 820A and 820B, respectively, and comprise a trigger generatingdevice 811 for timing the acquisition of the digital bus signal, adigital storage 812 for storing the data of acquired digital bus signal,and a display 813 for displaying the data.

[0010] The logic analyzers 810A and 810B observe the buses 820A and820B, respectively, as shown in Figure 8. The logic analyzers 810A and810B are interconnected externally, in which the logic analyzer 810B istriggered upon a synchronizing signal from the logic analyzer 810A.

[0011] In Published Unexamined Japanese Patent Application No.11-344511, a technique regarding a logic analyzer probe circuit that isinterposed between the logic analyzer and a measured circuit measured bythe logic analyzer was disclosed.

[0012]Figure 9 is a block diagram showing the configuration of the logicanalyzer probe circuit as described in the above patent.

[0013] Referring to Figure 9, this logic analyzer probe circuit 910comprises a probe circuit 911 for converting a signal input from ameasurement point of a measured circuit 920 into electricalspecification and outputting the converted signal, and a logic operationsection (programmable gate array) 912 for inputting an output signalfrom the probe circuit 911, making a predetermined logical operation onthe signal, and outputting a result of logical operation to a logicanalyzer 930.

[0014]Figure 10 is a block diagram showing the configuration of a PCIbus monitor as another conventional digital signal measuring apparatus.

[0015] In Figure 10, if a bus monitor device 1010 is inserted into a PCIbus 1020 of a system to be measured, the bus monitor device 1010acquires a digital bus signal passed on the PCI bus 1020, and stores thedata of measurement result in a digital storage (SRAM) 1011 mounted inthe bus monitor device 1010. After the end of measurement, themeasurement result stored in the digital storage 1011 is transferred toa computer as an analyzer connected externally, and the computerexecutes a specific analysis program to produce the analysis result.

[0016] However, with a recent increase in the system bus width, the dataamount that must be stored per unit time in measurement of the digitalbus has become enormous.

[0017] From only the viewpoint of the data amount to be stored, anexternal storage (e.g., magnetic disk) may be additionally mountedoutside the measuring apparatus, but when the system bus clock is fast,the data can not be written without delay because the external storagehas a low write rate. Therefore, there is a need that the measuringapparatus mounts a digital storage (e.g., semiconductor memory) capableof writing fast internally.

[0018] The fast digital storage is expensive, and physically mountablewith a limited capacity. Accordingly, in the present situation where theamount of data to be stored increases, the conventional digital signalmeasuring apparatus is difficult to perform the continuous observationand evaluation over the long time.

[0019] On one hand, for the evaluation and analysis of the total system,it is indispensable to make the observation over the long time. Also, itis indispensable to detect an unexpected bus event that must be observedover the long time to discover and evaluate its operation.

[0020] The conventional digital signal measuring apparatus acquired adigital bus signal on the bus, stored it in the digital storage,analyzed the stored digital bus signal to extract a bus event, andobserved the signal traffic on the bus. Therefore, it was impossible toobserve the signal traffic on the bus in real time in accordance withthe operation of the system to be measured.

[0021] Further, in case of observing plural buses, due to the recentincrease in the bus width, there are some instances where the number ofbuses to be measured exceeds the number of probes mountable on one logicanalyzer. In this case, a plurality of logic analyzers are prepared,interconnected externally, and synchronized, as shown in Figure 8.

[0022] However, the external connection through the cable is liable toproduce more noise to cause the malfunction as the signal frequency isincreased.

Summary of Invention

[0023] A feature of the preferred embodiments is to provide a digitalsignal measuring apparatus that can measure the signal traffic on a busover the long time in a complex system having plural buses.

[0024] Another feature of the preferred embodiments is to detect andevaluate an unexpected bus event as issued rarely.

[0025] It is yet another feature of the preferred embodiments to observethe signal traffic on a bus in real time in accordance with an operationof the system to be measured.

[0026] Moreover, it is still another feature of the preferredembodiments to provide a digital signal measuring apparatus that canobserve the signal traffic, even when plural buses are observed, withouthaving a plurality of digital signal measuring apparatuses connectedexternally.

[0027] In order to accomplish the above features, this inventioninvolves extracting a bus event from a digital bus signal on the bus ofthe system to be measured and processing the occurrence information ofthe bus event without directly storing or processing the digital bussignal. Thereby, the amount of information to be dealt with is reduced,and the observed result is displayed on the display at any time (in realtime), or the continuous observation over the long time is enabled.

[0028] Various other objects, features, and attendant advantages of thepresent invention will become more fully appreciated as the same becomesbetter understood when considered in conjunction with the accompanyingdrawings, in which like reference characters designate the same orsimilar parts throughout the several views.

Brief Description of Drawings

[0029]Figure 1 is a block diagram showing the configuration of a digitalsignal measuring apparatus according to an embodiment of the presentinvention.

[0030]Figure 2 is a block diagram showing the configuration of a busprobe device in this embodiment.

[0031]Figure 3 is a diagram showing the configuration of a counter unitin this embodiment.

[0032]Figure 4 is a chart for explaining the relation between theoccurrence situation of bus event and the read timing of the count valueof counter in the counter unit.

[0033]Figure 5 is a block diagram showing the configuration forobserving the signal traffic through the CPU bus and the PCI bus in thisembodiment, in which the system to be measured is a computer system ofIA-32.

[0034]Figure 6 is a diagram for explaining the operation of a bus eventdecoder unit in accordance with an occurrence situation of bus eventthrough the PCI bus in Figure 5.

[0035]Figure 7 is a diagram for explaining the operation of a bus eventdecoder unit in accordance with an occurrence situation of bus eventthrough the CPU bus in Figure 5.

[0036]Figure 8 is a block diagram illustrating the configuration of aconventional logic analyzer.

[0037]Figure 9 is a block diagram illustrating the configuration of aconventional logic analyzer probe circuit.

[0038]Figure 10 is a block diagram illustrating the configuration of aPCI bus monitor as another conventional digital signal measuringapparatus.

Detailed Description

[0039] This invention provides a digital signal measuring apparatuscomprising observing means for observing a bus event occurring on a busof a system to be measured, storage means for storing the informationregarding the occurrence of the bus event observed by the observingmeans, and processing means for processing the information regarding theoccurrence of the bus event stored by the storage means.

[0040] Herein, the observing means comprises a probe for acquiring adigital bus signal on the bus, and a decoder for decoding the digitalbus signal acquired by the probe into a bus event an object to beobserved. Preferably, the decoder is realized by PLD (Programmable LogicDevice).

[0041] Also, the storage means comprises a counter for counting thenumber of occurrences of bus event extracted by the observing means foreach type of bus event, and a control section for reading a count valueof the counter in response to a request from the processing means andsending the count value to the processing means.

[0042] Herein, a plurality of observing means may be providedcorresponding to the number of buses in the system to be measured, inwhich the counter of the storage means counts the number of occurrencesof bus event extracted by each of the plurality of observing means, andthe processing means analyzes the correlation of plural buses based onthe number of occurrences of bus event on the plural buses counted bythe storage means.

[0043] The processing means may comprise a data processing section foranalyzing the information regarding the occurrence of bus event acquiredfrom the storage means, and a display section for visually displayingthe result analyzed by the data processing section.

[0044] Also, the invention provides a digital signal measuring apparatuscomprising a probe unit for acquiring a digital bus signal on a bus of asystem to be measured, a decoder unit for extracting a bus event fromthe digital bus signal acquired by the probe unit, and a counter unitfor counting the number of occurrences of bus event extracted by thedecoder unit.

[0045] Moreover, the invention provides a digital signal measuringapparatus comprising observing means for acquiring a digital bus signalon a bus of a system to be measured and observing the occurrence of abus event based on the digital bus signal, and information processingmeans for processing the information regarding an occurrence situationof the bus event observed by the observing means and displaying theprocessed information as the image at any time.

[0046] Herein, the information processing means may analyze theoccurrence situation of bus event acquired from plural buses in thesystem to be measured and the correlation of the plural buses, anddisplays the analyzed result as the image at any time.

[0047] Moreover, this digital signal measuring apparatus may furthercomprise storage means for storing the information regarding theoccurrence situation of bus event observed by the observing means.

[0048] Also, this invention provides a traffic observing method forobserving the signal traffic on a bus of a system to be measured,comprising a step of acquiring a digital bus signal on the bus, a stepof generating a trigger signal indicating an occurrence of the bus whenthe acquired digital bus signal is matched with a preset signal patterndefining a bus event, a step of counting the number of occurrences ofbus event based on the generated trigger signal, and a step of analyzingthe signal traffic on the bus based on the result of counting the numberof occurrences of bus event.

[0049] More preferably, this traffic observing method may furthercomprise a step of generating the image data visualizing the analysisresult of the signal traffic and displaying it at any time.

[0050] Herein, the step of analyzing the signal traffic furthercomprises a step of analyzing the count result of bus events acquiredfrom plural buses and generating the information indicating thecorrelation of the plural buses.

[0051] Also, the step of counting the number of occurrences of bus eventmay comprise a step of receiving the trigger signal and counting it witha counter provided corresponding to the trigger signal, and a step ofsuccessively reading the count values of all the counters atpredetermined timings and storing them in a buffer, and the step ofanalyzing the signal traffic may comprise a step of analyzing the signaltraffic on the bus using the count values within the buffer afterstoring the count values of all the counters in the buffer.

[0052] The preferred embodiments of the present invention will bedescribed below in detail with reference to the accompanying drawings.

[0053]Figure 1 is a block diagram showing the configuration of a digitalsignal measuring apparatus according to an embodiment of the invention.

[0054] Referring to Figure 1, the digital signal measuring apparatus ofthis embodiment comprises a bus probe device 10, a traffic measuringapparatus 20, and a console unit 30. A trigger data communications line40 connecting the bus probe device 10 and a traffic measuring apparatus20, and a measured data communications line 50 connecting the trafficmeasuring apparatus 20 and the console unit 30 are through the fastparallel transfer or serial transfer, using the USB, IEEE1394 orIEEE1284.

[0055] The bus probe device 10 is connected to a bus provided in asystem to be measured 100, and functions as a measuring apparatus of abus event occurring on the bus. That is, the bus probe device 10acquires a digital bus signal on the bus, extracts a bus event from thedigital bus signal, generates a signal indicating an occurrence of thebus event, and sends it to the traffic measuring apparatus 20. Also, thebus probe device 10 always observes a bus clock and transmits it to thetraffic measuring apparatus 20 to hold a time series of counter triggersignals.

[0056]Figure 2 is a block diagram showing the configuration of the busprobe device 10.

[0057] Referring to Figure 2, the bus probe device 10 of this embodimentcomprises an input section 11 for latching a digital bus signal from thebus of the system to be measured 100, a bus event decoder unit 12 fordecoding the digital bus signal latched by the input section 11 into abus event, a communication unit 13 for sending the occurrenceinformation of bus event decoded by the bus event decoder unit 12 to thetraffic measuring apparatus 20, and a probe control unit 14 forcontrolling the bus event decoder unit 12 and the communication unit 13.

[0058] The input section 11 is a probe unit connected to the bus of thesystem to be measured 100, and is identical to the probe usuallyemployed to latch the digital bus signal. This probe is made of a highimpedance material to suppress the influence on the system to bemeasured 100 as much as possible.

[0059] The bus event decoder unit 12 is realized by a PLD, for example,to extract a bus event as observing object from the digital bus signallatched by the input section 11. Namely, using table collation means, itis determined whether or not an observation event has occurred, based onthe digital bus signal acquired by the input section 11. If the digitalbus signal acquired by the input section 11 is matched with a presetsignal pattern defining a bus event, a counter trigger signal indicatingthat the bus event has occurred is output. This counter trigger signalis output for each bus event. Accordingly, if the bus event decoder unit12 is set to observe n kinds of bus event, n counter trigger signals areoutput. The counter trigger signal is sent from the communication unit13 via the trigger data communications line 40 to the traffic measuringapparatus 20 for each bus event.

[0060] A plurality of bus probe devices 10 may be provided to extractthe bus events on plural buses in the system to be measured 100, asshown in Figure 1. In this case, each bus probe device 10, which has thesame constitution, generates a counter trigger signal, based on a busevent occurring on each bus, and sends it with the bus clock via thetrigger data communications line 40 to the traffic measuring apparatus20.

[0061] In the above manner, in this embodiment, the bus probe device 10not only acquires the digital bus signal, but also decodes the digitalbus signal into a bus event and sends the bus event to the trafficmeasuring apparatus 20. Accordingly, there is no step of transmittingthe digital bus signal via the outside cable, whereby it is possible tosuppress the occurrence of noise as much as possible. Since the digitalbus signal is not directly sent to the traffic measuring apparatus 20,but converted into the occurrence information of bus event and sent tothe traffic measuring apparatus 20, a signal (counter trigger signal)notifying that a predetermined bus event has occurred is sent, uponoccurrence of predetermined bus event, leading to great reduction in theinformation amount to be processed in the traffic measuring apparatus20.

[0062] The traffic measuring apparatus 20 stores the informationregarding the occurrence of bus event observed in the bus probe device10. Specifically, the number of occurrences of bus event is countedbased on the counter trigger signal sent from the bus probe device 10.And the count result (measured data) is sent back to the console unit30, upon a request from the console unit 30.

[0063] Referring to Figure 1, the traffic measuring apparatus 20comprises a probe communication unit 21 for communicating with the busprobe device 10, a counter unit 22 for counting the number ofoccurrences of bus event, a console communication unit 23 forcommunicating with the console unit 30, and a measuring apparatuscontrol unit 24 for controlling the overall operation of the trafficmeasuring apparatus 20.

[0064] The probe communication unit 21 receives a counter trigger signalsent from the communication unit 13 of the bus probe device 10, andoutputs it to the counter unit 22. This probe communication unit 21serves as a buffer for synchronizing the counter trigger signal with thecounter unit 22. Also, the probe communication unit 21 can accept aninput of counter trigger signal from the plurality of bus probe devices10.

[0065] The counter unit 22 inputs a counter trigger signal from theprobe communication unit 21, and updates the counter value correspondingto the input counter trigger signal. Thereby, the number of occurrencesof bus event indicated by the counter trigger signal is counted.

[0066]Figure 3 is block diagram showing the configuration of the counterunit 22.

[0067] Referring to Figure 3, the counter unit 22 comprises a clockcounter 22a for receiving and counting a clock signal (bus clock) sentfrom the bus probe device 10, a counter 22b for receiving and countingthe counter trigger signal, a clock buffer 22c for temporarily storingthe count value of the clock counter 22a and the buffer 22d fortemporarily storing the count value of the counter 22b, and a countercontrol unit 22e for controlling the counters and buffers (hereinafterabbreviated as counters 22a, 22b and buffers 22c, 22d, unless it isspecifically necessary to distinguish between the clock counter 22a andthe counter 22b, and the clock buffer 22c and the buffer 22d).

[0068] The counter 22b and the buffer 22d are provided corresponding tothe number of counter trigger signals sent from the bus probe device 10,or the number of bus events observed in the bus probe device 10, asshown in Figure 3. Thereby, the number of occurrences is counted foreach bus event observed in the bus probe device 10.

[0069] The counter control unit 22e copies the count values of the clockcounter 22a and the counters 22b to the clock buffer 22c and thecorresponding buffers 22d in accordance with a control signal from themeasuring apparatus control unit 24. After the count values of the clockcounter 22a and all the counters 22b are read, the count values held inthe clock buffer 22c and the buffers 22d are output to the consolecommunication unit 23.

[0070] A counter trigger signal from the plurality of bus probe devices10 may be input into the counter unit 22 via the probe communicationunit 21. In this case, a set of counters 22a, 22b and buffers 22c, 22das shown in Figure 3 is provided for each bus. In the counter unit 22,it is unnecessary to specifically distinguish between the buses, but thecorresponding counters 22a, 22b may count up for each signal.

[0071] In this embodiment, it is possible to cope with the increasednumber of buses as measuring object by adding the counters 22a, 22b andthe buffers 22c, 22d in the counter unit 22. Thus, the measuring unit isreadily extensible, without need of connecting externally a plurality ofdigital signal measuring apparatuses as in the conventional logicanalyzer. Thereby, it is possible to suppress the occurrence of noisecausing the malfunction.

[0072] The console communication unit 23 accepts a request from theconsole unit 30, and sends the measured data (count value) received fromthe clock buffer 22c and the buffers 22d of the counter unit 22 via themeasured data communications line 50 back to the console unit 30.

[0073] The measuring apparatus control unit 24 controls the overalloperation of the traffic measuring apparatus 20, but specificallycontrols the operation of sending back the measured data in the counterunit 22 and the consol communication unit 23. Namely, if the consolecommunication unit 23, upon accepting a read request of measured datafrom the console unit 30, sends a control signal to the counter controlunit 22e of the counter unit 22, which then copies the count values ofthe clock counter 22a and the counters 22b to the clock buffer 22c andthe buffers 22d, and outputs them to the console communication unit 23.And the console communication unit 23 sends the measured data (countvalues) to the console unit 30.

[0074] The console unit 30 is realized on a computer such as a personalcomputer or a workstation, and comprises a processing unit (CPU) 31 forprocessing the measured data received from the traffic measuringapparatus 20, a display unit 32 for displaying the processed result bythe processing unit 31, and a storage unit (digital storage) 33 such asa magnetic disk for storing the processed result by the processing unit31.

[0075] The processing unit 31 executes an analysis program for analyzingthe bus event in the system to be measured 100. Thereby, the processingunit 31 sends a read request of measured data (count value of thecounter unit 22) indicating an occurrence situation of bus event to thetraffic measuring apparatus 20 at a predetermined timing. Furthermore,the processing unit 31 analyzes the measured data sent back upon theread request, and stores the analysis result in the storage unit 33, aswell as creating the image data visualizing the analysis result anddisplaying it on the display unit 32.

[0076] At a stage where the traffic measuring apparatus 20 counts thenumber of occurrences of bus event, the information regarding the signaltraffic, such as when the bus event occurred, or how frequently the busevent occurs, can not be obtained. Accordingly, in this embodiment, theconsole unit 30 acquires the measured data (count value) from thetraffic measuring apparatus 20 periodically or at any timing, therebyobtaining the information regarding the signal traffic in the bus, alongwith the time information at which the measured data is acquired.Namely, if the number of occurrences of each bus event indicated by themeasured data is compared with the time (acquisition time) of acquiringthe measured data, it is possible to recognize which bus event hasoccurred how many times in a period from one acquisition time to anotheracquisition time.

[0077] In this embodiment as described above, in the bus probe device 10and the traffic measuring apparatus 20, a digital bus signal on the busof the system to be measured 100 is decoded into a bus event, and theoccurrence information of the bus event is only sent to the console unit30. Accordingly, the console unit 30 does not need to store and processthe digital bus signal, and can directly analyze the occurrenceinformation of the acquired bus event. Therefore, the console unit 30 inthis embodiment can display the analysis result at any time (in realtime) on the display unit.

[0078] Moreover, the information to be handled is not the digital bussignal itself, but the occurrence information of bus event, whereby theamount of information to be processed can be greatly reduced. Therefore,the information obtained over longer time can be stored in the storageunit 33, as compared with the conventional logic analyzer. Accordingly,it is possible to observe the signal traffic on the bus in the system tobe measured 100 over long time and in continuous basis. Thereby, the busevent occurring rarely can be observed and detected.

[0079] Also, the processing unit 31 analyzes the occurrence situation ofbus event on plural buses, and generates the information indicating thecorrelation of signal traffic on those buses. For the correlation, aprocess of creating the image data visualizing the correlationinformation and displaying the image data on the display unit 32 can beperformed in real time.

[0080] The above configuration is only illustrative of one preferredembodiment of the invention, and a difference in the constitutionregarded as a simple design change may be included within a technicalscope of the invention.

[0081] For example, in the above configuration, the buffers 22c, 22d fortemporarily storing the count values read from the counters 22a, 22b ofthe counter unit 22 are provided in the counter unit 22 itself, but maybe provided separately from the counter unit 22, or in the consolecommunication unit 23.

[0082] The input section 11 in the bus probe device 10 and the bus eventdecoder unit 12 do not need to be configured integrally. With a view toreducing the information amount of processing object by decoding thedigital bus signal into the bus event and processing or storing the busevent, rather than directly processing or storing the digital bussignal, the bus event decoder unit 12 may be interposed between theprobe corresponding to the input section 11 and the traffic measuringapparatus 20 of this embodiment, or the probe and the bus event decoderunit 12 may be connected via the external cable.

[0083] In the embodiment with the above configuration, an operation ofobserving the event occurring on the bus and measuring the signaltraffic on the bus will be described below.

[0084] The bus events occurring on the bus are denoted as event-1, 2, 3(hereinafter abbreviated as E-1, E-2 and E-3). The bus event decoderunit 12 of the bus probe device 10 sends a counter trigger signalcorresponding to each bus event (hereinafter denoted as T-1, T-2 and T-3for corresponding bus event) to the traffic measuring apparatus 20, whenobserving each bus event E-1, E-2 and E-3. If the counter unit 22 of thetraffic measuring apparatus 20 receives the counter trigger signal T-1,T-2 and T-3, it increments the count value of corresponding counter 22b(hereinafter denoted as C-1, C-2 and C-3 corresponding to the countertrigger signal).

[0085]Figure 4 is a chart for explaining the relation between theoccurrence situation of bus event and the read timing of count value ofthe counter 22b in the counter unit 22.

[0086] The bus probe device 10 always observes the bus clock in thesystem to be measured 100 and sends it to the traffic measuringapparatus 20. Also, the clock counter 22a of the counter unit 22receives the clock signal from the bus probe device 10 and counts up thenumber of clocks (hereinafter this number of clocks is denoted as CLK).

[0087] If E-1 is detected by the bus event decoder unit 12 of the busprobe device 10 at time t₁, T-1 corresponding to E-1 is sent from thebus probe device 10 to the traffic measuring apparatus 20, andcorresponding C-1 is counted up in the counter unit 22.

[0088] Then, if a read request of the measured data is issued from theconsole unit 30 to the traffic measuring apparatus 20 at time t₁', CLK,C-1, C-2 and C-3 of each counter 22a, 22b are copied onto thecorresponding buffer 22c, 22d in the counter unit 22. And the value ofthe buffer 22c, 22d is locked till the CLK, C-1, C-2 and C-3 are readfrom the buffer 22c, 22d, and sent to the console unit 30. Upon a readrequest from the console unit 30, CLK, C-1, C-2 and C-3 are read fromthe buffer 22c, 22d, and the buffer 22c, 22d is unlocked.

[0089] Then, if E-3 is detected by the bus event decoder unit 12 of thebus probe device 10 at time t₂, T-3 corresponding to E-3 is sent fromthe bus probe device 10 to the traffic measuring apparatus 20, and thecorresponding C-3 is counted up in the counter unit 22.

[0090] Then, if a read request of the measured data is issued from theconsole unit 30 to the traffic measuring apparatus 20 at time t₂', CLK,C-1, C-2 and C-3 of each counter 22a, 22b are copied onto thecorresponding buffer 22c, 22d in the counter unit 22. And the value ofthe buffer 22c, 22d is locked till the CLK, C-1, C-2 and C-3 are readfrom the buffer 22c, 22d, and sent to the console unit 30. Upon a readrequest from the console unit 30, CLK, C-1, C-2 and C-3 are read fromthe buffer 22c, 22d, and the buffer 22c, 22d is unlocked.

[0091] In the console unit 30, evaluating a difference between the countvalues indicating the number of occurrences of measured data bus eventsacquired at time t₁' and time t₂', CLK indicates the number of clocksfrom t₁' to t₂', C-3 is incremented by one, and other counters areunchanged. From this analysis result, it can be recognized that one busevent was issued in the bus from t₁' to t₂'. The actual time intervalfrom time t₁' to time t₂' is equal to (t₂ - t₁)/clock frequency.

[0092] A specific example of the system to be measured 100 as thecomputer in this embodiment will be described below.

[0093]Figure 5 is a block diagram showing the configuration forobserving the signal traffic on the CPU bus and PCI bus in thisembodiment, in which the system to be measured 100 is the computersystem of IA-32. Figure 6 is a diagram for explaining the operation of abus event decoder unit 12 in accordance with an occurrence situation ofbus event through the PCI bus in Figure 5. Figure 7 is a diagram forexplaining the operation of the bus event decoder unit 12 in accordancewith an occurrence situation of bus event through the CPU bus in Figure5.

[0094] The computer system as the system to be measured 100 mounts aPentium^(®) III processor of Intel Inc., in the United States as theCPU, and comprises the CPU bus and the PCI bus connected via a CPU-PCIbridge to the CPU bus, as shown in Figure 5. The bus probe device 10 isconnected to each of the CPU bus and the PCI bus to observe a digitalbus signal on each of the CPU bus and the PCI bus. And in the bus eventdecoder unit 12 of the bus probe device 10, a bus event occurring oneach of the CPU bus and the PCI bus is extracted, and a counter triggersignal is sent to the traffic measuring apparatus 20.

[0095] The traffic measuring apparatus 20 accepts the counter triggersignal, and counts the number of occurrences of bus event in the counterunit 22. And this count value is sent to the console unit 30 andprocessed.

[0096] In the configuration as shown in Figure 5, the traffic measuringapparatus 20 and the console unit 30 are USB connected, and the USBcable is employed as the measured data communications line 50.

[0097] Referring to Figure 6, three kinds of signals, bus clock (CLK),FRAME# and C/BE#, as the PCI bus signal are input into the bus eventdecoder unit 12. Four C/BE# signals from C/BE[0]# to C/BE[3]# are input,and seven kinds of events (Memory Read, Memory Read Line, Memory ReadMultiple, Memory Write, Memory Write and Invalidate, I/O Read, I/OWrite) are detected in accordance with the values of four C/BE# signals.And a counter trigger signal (Trigger-1 to Trigger-7) is output for eachevent.

[0098] Referring to Figure 7, three kinds of signals, bus clock (CLK),ADS# and REQ#, as the CPU bus signal are input into the bus eventdecoder unit 12. Five REQ# signals from REQ[0]# to REQ[4]# are input,and seven kinds of events (I/O Read, I/O Write, Memory Read andInvalidate, Memory Code Read, Memory Data Read, Memory Write, MemoryWrite Back) are detected in accordance with the values of five REQ#signals. And a counter trigger signal (Trigger-1 to Trigger-7) is outputfor each event.

[0099] As described above, with this invention, it is possible tomeasure the signal traffic on the bus over the long time in a complexsystem having plural buses by reducing the amount of information to bedealt with in the digital signal measuring apparatus.

[0100] Thereby, it is possible to detect and evaluate an unexpected busevent as issued rarely.

[0101] Also, it is possible to observe the signal traffic on the bus inreal time in accordance with an operation of the system to be measuredby decoding a digital bus signal on the bus into a bus event.

[0102] Moreover, it is possible to provide an apparatus constitutionthat can observe the signal traffic, even when plural buses areobserved, without having a plurality of digital signal measuringapparatuses connected externally.

[0103] It is to be understood that the provided illustrative examplesare by no means exhaustive of the many possible uses for my invention.

[0104] From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention and, withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

[0105] It is to be understood that the present invention is not limitedto the sole embodiment described above, but encompasses any and allembodiments within the scope of the following claims:

Claims 1.A digital signal measuring apparatus comprising: observingmeans for observing a bus event occurring on a bus of a system to bemeasured; storage means for storing the information regarding theoccurrence of the bus event observed by said observing means; andprocessing means for processing the information regarding the occurrenceof the bus event stored by said storage means. 2.The digital signalmeasuring apparatus according to Claim 1, wherein said observing meanscomprises a probe for acquiring a digital bus signal on said bus, and adecoder for decoding the digital bus signal acquired by said probe intoa bus event an object to be observed. 3.The digital signal measuringapparatus according to Claim 1, wherein said storage means comprises acounter for counting the number of occurrences of bus event extracted bysaid observing means for each type of bus event, and a control sectionfor reading a count value of said counter in response to a request fromsaid processing means and sending the count value to said processingmeans. 4.The digital signal measuring apparatus according to Claim 3,wherein a plurality of observing means are provided corresponding to thenumber of buses in said system to be measured, said counter of saidstorage means counts the number of occurrences of bus event extracted byeach of the plurality of observing means, and said processing meansanalyzes the correlation of plural buses based on the number ofoccurrences of bus event on said plural buses counted by said storagemeans. 5.The digital signal measuring apparatus according to Claim 1,wherein said processing means comprises a data processing section foranalyzing the information regarding the occurrence of bus event acquiredfrom said storage means, and a display section for visually displayingthe result analyzed by said data processing section. 6.A digital signalmeasuring apparatus comprising: a probe unit for acquiring a digital bussignal on a bus of a system to be measured; a decoder unit forextracting a bus event from the digital bus signal acquired by saidprobe unit; and a counter unit for counting the number of occurrences ofbus event extracted by said decoder unit. 7.The digital signal measuringapparatus according to Claim 6, wherein said decoder unit is a PLD(programmable logic device). 8.A digital signal measuring apparatuscomprising: observing means for acquiring a digital bus signal on a busof a system to be measured and observing the occurrence of a bus eventbased on said digital bus signal; and information processing means forprocessing the information regarding an occurrence situation of the busevent observed by said observing means and displaying the processedinformation as the image at any time. 9.The digital signal measuringapparatus according to Claim 8, wherein said information processingmeans analyzes the occurrence situation of bus event acquired fromplural buses in said system to be measured by said observing means andthe correlation of said plural buses, and displays the analyzed resultas the image at any time. 10.The digital signal measuring apparatusaccording to Claim 8, further comprising storage means for storing theinformation regarding the occurrence situation of bus event observed bysaid observing means. 11.A traffic observing method for observing thesignal traffic on a bus of a system to be measured, comprising: a stepof acquiring a digital bus signal on said bus; a step of generating atrigger signal indicating an occurrence of said bus when said acquireddigital bus signal is matched with a preset signal pattern defining abus event; a step of counting the number of occurrences of bus eventbased on said generated trigger signal; and a step of analyzing thesignal traffic on said bus based on the result of counting said numberof occurrences of bus event. 12.The traffic observing method accordingto Claim 11, further comprising a step of generating the image datavisualizing the analysis result of said signal traffic and displaying itat any time. 13.The traffic observing method according to Claim 11,wherein said step of analyzing the signal traffic further comprises astep of analyzing the count result of bus events acquired from pluralbuses and generating the information indicating the correlation of saidplural buses. 14.The traffic observing method according to Claim 11,wherein said step of counting the number of occurrences of bus eventcomprises a step of receiving said trigger signal and counting it with acounter provided corresponding to said trigger signal, and a step ofsuccessively reading the count values of all the counters atpredetermined timings and storing them in a buffer, and said step ofanalyzing said signal traffic comprises a step of analyzing the signaltraffic on said bus using the count values within said buffer afterstoring the count values of all the counters in said buffer.